Air Conditioning - AC dryer question

I recently had a "spring checkup" from a local AC firm and the tech promoted a $500 followup service call. The cold line from the compressor was frosting up a little on the outside and when he put a temperature sensor on it the reading was 29 degrees before the dryer and 32 or 33 after the dryer. He said there should be negligible temperature change - a 4 degree difference meant the dryer was partially clogged and if if became completely clogged MAJOR repair expenses would follow. I'm comfortable with the cost for replacing the dryers (one on each line) - but, IS the 4 degree temperature change a sign of trouble or is it normal?

thats a suction line dryer your talking about sounds odd to be on a residential unit unless you had a compressor change done.that line temperature is low for a returning suction line from the air handler........do you have any ice on the insulate line from the inside coming out of the furnace.did you notice the days temperture when he did his running check of the dryer temp differences?

With a partially clogged filter-drier there would be a temp. drop across the drier. I think he got the readings wrong. In any event, the difference is not great enough to worry about.
29* from the evaporator is low. Did he clean the coil? Change the filter(s)?
Tom Beer 4U2

Sorry about the delayed response - it's been raining for 4 days here and I needed to go look at the unit again. The condensor unit in question was replaced summer of 2003 due to storm damage - it appears there are dryer units on both lines. It was probably 65-70 outside when the checkout was done in late March. There was slight visible frosting on the insulated suction line where the insulation was opened by the tech. Tech worked inside first and replaced filter but didn't open the unit and look at the evaporator coil at all, then turned thermostat on and spent probably 1-2 hrs cleaning the 2 condensor units (looked like new when he was finished) while the outside disconnects were pulled. Then connected condensor to check it out - that's when he raised the issue of line temps. His opinion was that a 4 degree temp change at the suction line dryer was a sign the dryer was somewhat clogged and should be replaced before it stopped up completely. If that is a reasonable recommendation, I'd rather do that than risk wrecking the condensor. I figured any experienced AC tech should know whether the 4-degree temperature change justified the corrective action or not. (The tech seemed knowledgable, but pretty young - and AWFUL focused on physically scrubbing the condensors to make 'em look like new)

on any system commercial or residential any remaining liquid coming down the suction line is potential damager to the compressor .he might of been picking up liquid metering thru it...no swet as long as your suction reading is 55-68PSI depending on the air across the evap your:cool:coooool:cool: enjoy the summer.if you start to see ice on the out side going to the condenser no calls needed.:thumbup:

Sorry about the delayed response - it's been raining for 4 days here and I needed to go look at the unit again. The condensor unit in question was replaced summer of 2003 due to storm damage - it appears there are dryer units on both lines. It was probably 65-70 outside when the checkout was done in late March. There was slight visible frosting on the insulated suction line where the insulation was opened by the tech. Tech worked inside first and replaced filter but didn't open the unit and look at the evaporator coil at all, then turned thermostat on and spent probably 1-2 hrs cleaning the 2 condensor units (looked like new when he was finished) while the outside disconnects were pulled. Then connected condensor to check it out - that's when he raised the issue of line temps. His opinion was that a 4 degree temp change at the suction line dryer was a sign the dryer was somewhat clogged and should be replaced before it stopped up completely. If that is a reasonable recommendation, I'd rather do that than risk wrecking the condensor. I figured any experienced AC tech should know whether the 4-degree temperature change justified the corrective action or not. (The tech seemed knowledgable, but pretty young - and AWFUL focused on physically scrubbing the condensors to make 'em look like new)

I and most techs I know would consider a four degree drop across a drier as HUGE, requiring action. The drier on the suction (bigger line) would just need to be cut out and piped in, not replaced. The drier on the liquid (smaller line) should be replaced.

The suction filter-drier could be a little clogged from junk left from the change-out in '03. That can be removed and replaced with pipe, and the smaller F-D on the LL changed.
It'll take some time to recover the refrigerant, do the repairs, evacuate, and recharge with the same recovered refrigerant (if it smells ok).
And, if the LL F-D* is sweat in, the new one could be installed with flares to facilitate changing in the future without using a torch, nitrogen while brazing, and evacuating.
A small positive pressure left in the system while changing the flared LL F-D will keep any moisture laden ambient air from entering while the FD is being swapped.
While the system is open, an acid test should be performed.
*Liquid Line Filter-Drier
Tom Beer 4U2